Recent findings raise concern regarding the safety of mercury in dental amalgam. It is known that mercury can be released from amalgam by prolonged chewing. Also, it has been shown in vitro that methyl mercury can be formed by the action of Streptococcus sanguis, Streptococcus mutans or Streptococcus mitior on conventional and high copper admixed amalgams. But, no studies have been reported to determine if oral indigenous microflora will convert mercury to methyl mercury. This is of great importance to the dental profession since methyl mercury is more toxic than inorganic mercury. This study is designed 1) to determine if mercury and methyl mercury can be detected from blood and urine samples of dental patients with amalgam restorations at different time periods after the initial dental visit up to a duration of one year, 2) to correlate the concentrations of mercury and methyl mercury, if detected, to the number, surface area and duration of amalgam restorations and 3) to determine if the level of mercury and methyl mercury that can be detected is within the range of maximum allowable limits. The occlusal surface area of each amalgam and the total amalgam surface area will be determined on models using a dissecting microscope with a digital analyzer. Mercury and methyl mercury will be determined by atomic absorption spectrophotometry. Our long term objectives include the continuation of this project for a period of two more years to determine if indeed significant amounts of mercury can be found in blood and urine of dental patient after amalgam restorations. Then we may be able to form some conclusions concerning the safety of mercury in amalgams. Furthermore, the removal of amalgam restorations for fear of mercury poisoning may be unnecessary. Conversely, if significant concentrations of mercury and methyl mercury are found, further studies will be conducted to determine the possible health implications of such concentrations.